Rubber-fiber article and process of making the same



Nov. 26, 1929. w, w sc T 1,737,133

RUBBER FIBER ARTICLE AND PROCESS OF MAKING THE SAME Filed July 12, 1 927 cords, threads or fibers of substantial len prising new rubber also particles of comminuted' .sisting mainly of Patented Nov. 26, 1929 UNITED STATES PATENT OFFICE WILLIAM vB.

'WEQCOTT, OF BOSTON, KASSACHUSETTfi,

ASSIGNOR TO RUBBER LATEX sacnusn'rrs RUBBER-TIBER ARTICLE AND PROCESS OF IAKING THE SAME Application filed July 12, 1927. Serial No. 205,256.

This invention relatesto rubber-fiber articles and recesses of making the same; and it comprises a relatively hard, dense and resilient rubber-fiber article comprising disposed in random arran ement, bgn ed together by a continuous bo y of rubber extending within and permeating said cords, threads or fibers, said body of rubber comderived in situ from liquid latex and prevulcanized rubber; and it further comprises a method of making such articles wherein compound articles of rubber and fabric or cord are disintegrated and separated in such manner as to give a fraction consisting mainly of rubber and a fraction contogether with as much of the rubber fraction as may be desired being impregnated with latex, (usually stabilized agalnst the coagulating efiect of the comminuted rubber by an added animal proteid), in such manner as to produce thorough wetting of all the fiber and the wet mass being molded to desired shape, dried and cured or vulcanized; all as more fully hereinafter set forth and as claimed.

One purpose of this invention is to produce a ton h resilient product suitable for heavy duty service, such as the absorption of treated in reclaiming plants as digestion with mechanical shock and vibration under reciprocating mechanisms and the like, industrial truck wheels and conveyor mechanism rollers, silent pads for caterpillar tractors, wheels for casters and the like, etc. in which great strength is obtained by rubber bonded cords or threads, while still having a limited resiliency. I y

The utilization of old compound fabric and rubber articles, such as'tire scrap, is a technical problem. Sometimes, the scrap is caustic soda solution to destroy the fiber and extract some of the sulfur,

ere is a waste of fiber. Before reclaiming, the fiber may be separated mechanically to a greater or less extent. This is practicable,

since in tires and the like the rubber and fiber fiber; the latter fraction,

a whole by or cords are largely positioned in different layers. In this mechanical separation, however, such rubber as clings to the fiber is wasted. Sometimes, the recovered fiber is comminuted to a flufi', flock or lint and the roduct then worked into rubber on the mill. I

ere, however, it serves only as a filler; it being impracticable by present day methods to work fiber of substantial length uniformly into high rade rubber on the mill. The length of milling required for uniform incorporation commmutes the fiber. In a thoroughly compounded article of this type, it is rare to find fiber having lengths greater than 0.10 inch. Fiber in flufi form stiflens the compound but adds nothing to the tensile strength of the final article; it is merely a filler. Cords or threads, in small amount, may be worked into rubber on the mill, particularly if softeners, such as oils, are used,

but the maximum amount of cord which can be milled into rubber is small and further the exterior only of the cord is wet by the rubber. This is also true of rubber cements,

that of the normal 30 per cent latex could contain not more than about 2 per cent of rubber. While it is true that the so-called rubbber solvents, benzol, gasoline, and the like, wet fiber more readily than does water, it is not possible to deposit, from a solution of rubber which is sufliciently fluid to permeate the cord, such an amount of rubber as is required to fill the'cord interstices, even when these arebrought to the irreducible minimum by compression so great as to be Lust short of compressive destruction of the fi er.

I have discovered that an amount of rubber sufficient to fill the voids in the cords, when the latter are subjected to such ressures as are commonly used incuring ru ber, can be deposited therein from normal latex while the cords are uncompressed and that a product may be so obtained in which all of the largely occurs in the ent purposes.

fiber within the cords isfbonded by the permeating rubber.

In the present invention, as in the acknowledged prior art, I perform a preliminary rough mechanical separation of fiber and rubber with tire scrap or similar material containin both rubber and cotton cord or fabric. n American tire scrap, fiber now form of cords; and suchscrap is the most desirable for the pres- The separated cords or fibers resulting from this mechanical separation are obtained in short pieces, averaging, for the most part, between 0.50 and 1.5 inches. There will be a percentage of fines and some longer cords or fiber; but the bulk of the fiber will be as stated. Fines and over-sized material can be mechanicall removed, if this be desired. In general, prefer to remove both fines and over-size, because the first, serving only as a filler, increases the amount of bonding rubber required without correspondingly increasing the strength or utility of the product, while the latter renders the desired. uniform random distribution of the fiber more diificult to secure.

In breaking up the scrap and comminuting, most of the rubber is torn away from'the her or cords and may be mechanically removed. It carries but a small fiber as arule and is sent to claiming apparatus.

In the present invention, I utilize the mechanically separated cords, and as much of the comminuted rubber asmay be desired, to produce hard, dense, resilient, molded shapes suitable for shock absorbers, wheels, casters and many other purposes.- With the best percentage of the rubber repracticable mechanical separation of the. tire 'not only the cords and the cords by a scrap, the cords will carry from 3 per cent to 5 per cent of adhering rubber, this rubber occurring as isolated spots or bodies. Tires and similar composite articles are made by frictioning and while there is a good mechanical union between the rubber and-the fabric or cords, the rubber does not extend within the fiber bundles forming the body of, the

cords or fabric. There is more of a locking union than of any -real cohesion. The individual lengths of cords usually retain much,

or most, of their original twist but in comminution their ends become rou hened and have a brushlike appearance. ostly, the cent to 5 the method of separation.

In the present invention I bond together,

particles of comminuted rubber,

continuous body of new rubber derived, in situ, from latex, this body of rubber being integral and extending through the -cords, threads or fiber bundles including the old rubber.

but the individual fibers within The old rubber particles, adhering to the cords or allowed to remain with the fiber, are surrounded and bonded by thenew preservative. Latex is readily coagulated b acid, by certain common rubber fillers, suc

as carbon black, asbestos, etc., and by vulcanized rubber, particularly when freshly comminuted or cut to exposeunoxidized surfaces. The coagulative eife'ct of comminuted rubber mav be prevented by small additions of animal proteid, particularly hemoglobin, as set forth in the Day application, Serial No. 158,828, which issued on October 20, 1928, as Patent No. 1,689,581. Hemoglobinis a proteid coagulable by heat and mg carefully dried articles containing hemoglobin it cures and adds to the strength of the bond as described in my copending application Serial No. 201,207, filed June 24, 1927. Mixtures containing latex protected b hemoglobin permit of the expression ot excess latex. from the cords, which are not sticky at this time. The wet mixture may be readily formed into desired shapes. Instead of a simple molding operation, the material containing latex treated with hemoglobin or the like, can be extruded in the form of a tubulus, which may be compressed and vulcanized.

In' practical embodiments of the present invention, I thoroughly wet the. fibrous fraction of the scrap with latex. This will give a suflicient amountof rubber for the resent purposes. This I usually accomplish y stir ring the soap fiber and rubber into an excess of latex. I sometimes preliminarily wet the fiber, particularly in the case of cords, withboiling water, express as much of this water as possible, by any convenient means such as a basket type centrifuge and then stir the thoroughly dam ened fiber into the latex. This expedites t e penetration 'of the latex without, however, causing too great a dilu-' tion. Another useful expedient, which howin' vulcanizever cannot be used unless a protective col- .loid, such as hemoglobin, has been added to the latex, is to pass the cords through rolls beneath the surface of the latex bath or to tumble the mass in an oscillatingperforated-cylinder partially submerged "in the latex bath, thus expelling the contained air and facilitating the penetration ofthe latex.

In any event, the cords are first thorou hly saturated with latex and then freed of excess latex, first using drainage and then an other convenient means. The basket centrifuge may be used for this latter purpose or the wet mass may be directly compressed in I usually dry to obtain a pervious mass car'- [mamas a perforated mold to express the excess latex and yield the desired shape at one operation.

This shape should approximate in two dimensions the size of'the contemplated product. 1

At this stage in the operation, I'have a wet molded mass carrying latex-saturated cordsand particles of prevulcanized rubber. This ryinga filmiform layer of latex rubber gel on all fiber andold rubber surfaces. Drying v is advantageously carried so far that the amount of moistureis lessthan the natural water of condition of the fiber.. While I usually referto dry to produce a gel of latex rub r, it is sometimes desirable to form a tough reticulate coagulum, which is con celerators are added to'the fluid latex before impregnation. oi the fiber. Ammonium pol sulphide may be used.

ul""ur cont ined in the latex, and intend-i ed for vulcaniaing purposes, exhibits inter- --esting properties. Even in the presence 0 an excess of fluid latex, substantially all of the sulfur introduced therewith remains in and on the fiber after expressionof the excesslatex. In practice, the requisite amountof sulfur, either as ordinary fine sulfur or combined sulfur or sulfur in a colloidal state, is mixed in with the fluid latex, or is weighed out with the fiber without regard to the latex excess. Practically none of the su lfur goes with the latexvwhicli is expressed. In this respect, the iatexbehaves in a different manner than the solvents employed for rubber cements.

The warm dried material as it comes from the dryer can be compressed in the final mold "and vulcanized. This compression; obliterates voids and 'converts the rubber, then existing to a large extent in film form as stated, into a continuous integral body. article so produced is of surprising mechanical strength and contains the new rubber in gel form; a form comparable inits curing characteristics to long milled raw rubber, as

stated.

Generally, I desire to produce vulcanized final articles. In this case,sulfur and ac-- celerators are incor orated' into the mass with the latex. Fillers can also be incorporated at this ti'me,,if desired. Comminuted prevulcanized rubber,-such as adheres to the cords in small amounts and a'simay be added predetermined amounts to the 'mix, tends The.

to c'oagulate the latex as stated, as do carbon black and certain other common rubber fillers and *pigments. As coagulation, even to the ;flocculent state, tends to prevent thorough impregnaton of the fiber bundles by the latex, I add an effective'protective colloid. Hemolobinis best, not only because it is effective in small amounts, 5 per cent on the latex rubpressures employed during vulcanization af- 7 feet the properties of the final product. In the I. resent invention, wherein a hard, but resilient material is usually sought, the cures may be relatively short, say for twenty minxutes with sixty pounds of steam or less. When the final product is to have a thickness of the order of an inch, the cure may. advantageously be accomplished by vulcanizing for twenty minutes with fifty pounds steam lpressure, using three per cent of sulfur. For

very thick articles, partialor stepcures are best. a y

A cure of this character, that is, a light cure for the latex-rubber bond, is, desirable so that the product shall be sensitive in re sponse to vibratory lcads. Longer cures with more sulfur render the article harder and less resilie'nhbuthave ,no appreciable advantageous efiect on the tensile strength. I have ound that between .10 per cent and 15 per cent by weight, of-latex rubber is required to cover all the fiber, surfaces and yield a continuous integral bond and-that,.with bonding rubber between these limits, acompressive force of aboutone ton to the square inch, at curing temperatures, is sufficient to obliterate completel the interstitial voids. With more bonding ru ber, less pressure is re- .quired, but, with less than about 10 per cent bonding rubber, the bond cannot be made continuous throughout the fiber mass; voids remain and .the product will absorb water in amounts much in excess of that taken up when there is a sufliciency of bond.

It is to be understood that a vulcanized article containing cords or threads that have wet the fibers. There are several distinctions Thus, amass of fibers cemented with ordmar rubber and solvent, I

between the two.

such as gasoline or t e like, hasa'lower 1 specific gravity than a similar mass of fibers treated with latex. The cemented article contains air pockets or voids between-the in dividual fibers, whereas, if latex be employed, these spaces are filled with bonding rubber.

: ber compounds and is ideally suited to mechanical purposes, in that, in the first instance it is that of a very high grade compound but the rate of resilient deformation changes very rapidly, as the cords come into play, until a high resistance is built u limited resilient deforma ility with great ultimate compressive resistance.

The process of this invention has, among its many advantages over the usual practice,

that of so'utili zing the material entering into the" product as to produce no waste or trimmings requiring reworking.

Theinvention as embodl d inan article of manufacture is characterized by the provis on of a relatively hard and dense article, that is,

composition of matter, but have claimed, in

. inches,

cords havinga length of from 0.50 to 1.5-

that of one having a hardness approaching which is yet resilient, that is,

hard rubber, is not brittle or unyielding Structurall the article is composed of a molded rub er and fiber composition, wherein the fibers occur ascords of appreciable length that are disposed in random arrangement and which are impregnated and bonded with vulcanized latex rubber.

Tlris application contains subject matter in common with my copending application Serial No. 67 8,67 3, filed December 5, 1923, which issued on October" 18, 1927, as Patent No. 1,645,635, wherein I have described a like the wet mass in a'form similar to t at oithe' article finally desired, drying the shaped article, compressing the article, and curing the article.

' 2. The process of making rubber-bonded fiber wheels which comprises mechanicallyseparating tire scrap and the like into fiber and rubber, saidfiber containing a small proportion of adhering rubber, mixing the fiber with vulcanizing materials, adding suflicient latex to thoroughly wet the mass, molding into a tubulus having about the diameter of the proposed \wheelbut several times as thick,

drying and vulcanizing in a mold under sufiicient pressure to obliterate the voids and produce the .wheel desired.

3. As an article of manufacture adapted to withstand high pressures and resilient to a limited extent a mass composed mainly of It has a sharply I like hard rubber.-

a mass of fibers in theform of cords hav-i inches disposed in interlocked and random arrangement and bonded with rubber derived,

in situ, from latex, molded to, shape and vulcanized.

4;. The method of making molded articlesof rubber and fiber which comprises shredding tire" scrap to provide cords of 0.50 to 1.50 C

saturating the 'c'ogds with rubber latex containing a protective colloid enablin complete saturating, .forming the saturate cords to a predetermined shape, dryin the mass and vulcanizing the same with t eaid of heatand pressure.

5. As an article of manufacture, a poreless shaped resilientmass adapted to withstand high. compression without deformation and inches in length, separatingthe cords drom the maj or portion of the rubber in the scrap,-

composed mainly of tire scrap containing cords between lengths of 0.50 to 1.50 inches bonded with vulcanized rubber derived in sit-u from rubber latex! 6. As an article of manufacture, a shaped mass oi randomly dis osed cords bonded- I interiorly and exterior y body of vulcanized rubber.

7. As an article or manufacture, having limited resiliency, a molded shape. composed by a continuous of randomly disposed cords and a minor [amount of vulcanized bonding rubber surrounding and permeating said cords.

I 8. As an article of manufacture having limited resiliency, a molded shape composed of randomly disposed cords and particles of compounded rubber bonded together by a continuous body of vulcanized rubber surrounding saidparticles of compounded rubber an permeating said cords.

9. limited resiliency containing comminute e process of making products of d v rubber-fiber articles bonded together by vulcanized rubber in minor amount which com prises preparing twisted fiber aggregates in the form of cords havinga length of substantially 0.5 to 1.5 inches and small particles or compounded vulcanized rubber from old tires, saturating the cords with rubber latex containing a protective colloid and a sufliciency of vulcanizing agents, expressing the excess latex, shaping the wet mass in a PllS- matic form similar 1n two dimensions to that of the article finally desired, drying the shaped article, compressing the article along the third dimension thereof and vulcanizing the article.

10. The method or making a rubber and.

fiber article which comprises admixing a quantity of twisted fiber aggregates containing yulcanized rubber with fluid latex containing bodies preserving it against coagulation by said vulcanized rubber and enabling permeation of saidaggregates by said latex, thereby making a wet plastic mass, shaping the wet mass into a form,'drying the mass r 'to-re'move water and to form a continuous bond or rubber derived from 1am bonding said. fiber aggre ates'and'vulcanized rubber 1 compressin ,sai dried sha to effect a final shape for t 0 article and o literate the voids I 5 left in drying and subjecting the compressed shape to vulcanization.

11. As a new article, a rubberbonded resil- I ient wheel adaptedto withstand high com- 'pression without deformation and composed 10 mainly of relatively short len he of twisted cord carryingrubber, said cor being bonded by an integral mass of vulcanized rubber derived from latex permeatin said cord, said latex containing a coa i118 proteid enablin permeation and orming part of the final nd,' the bonding rubber'car in isolated included masses of old rubber f ro an- 7 other source. y a

In testimony hereof, I have hereunto a0 alfixed my signature. B. WESCOTT 

